Update NL embeddings eval playground

[shifucun]

Remove golden stat vars and eval scores since these are not practical and reliable.

Updated this into a playground that can upload sv descriptions and queries on the fly and check stat var matches. The matches can highlight stat vars that have override descriptions.

[shifucun]

1. Wonder if we should have the query textbox before the NL description textbox? Because I can imagine this playground is helpful to try queries to see the variable matches for different models, as well, optionally, override/add NL descriptions?
2. Wonder if it might be good have a few lines to articulate what to do with the tool?

This playground can be used explore the variable matches given a few queries for different models. Additionally, you can also override or add NL descriptions for variables.

Swapped the order. I put the suggestions as text area instruction explicitly now.